1. Field of the Invention
The present invention relates to a control apparatus for vehicles which produce a driving force with a motor, and more specifically, a vehicular control apparatus with an improved parking lock release operation.
2. Description of the Related Art
In general, the parking lock units of automobiles are configured to lock the front reduction gear from rotating.
When an automobile is parked on a slope, the front wheels are still forced to rotate even in the parking lock state. Here, since the rotation of the front drive shaft is inhibited by the parking lock unit, the front drive shaft does not substantially rotate. However, a small torsional stress is exerted on the front shaft drive, and therefore actually, the automobile moves slightly when the parking lock is executed.
Then, when the parking lock is released, the torsion stress on the front drive shaft is released, which allows the front reduction gear and the front driving source to rotate abruptly. Because of such an abrupt rotation, vehicular passengers may feel a shock, producing a unpleasant feeling and discomfort.
Techniques for reducing shocks produced when releasing the parking lock such as above are disclosed in Publication 1 (Japanese Patent No. 4297135), Publication 2 (Jpn. Pat. Appln. KOKAI Publication No. 2009-143270) and the like.
Publication 1 teaches a technique of controlling the torque of an electric motor by estimating the torque due to torsion accumulated in a direct coupling range (the range maintained in a power transmission state to the driving wheels, which is on the automatic transmission or between the automatic transmission and driving wheels) while the motive power of the power source is being transmitted to the driving wheels, and controlling the torque of the electric motor based on the estimated torque due to torsion. With the technique of Publication 1, directed to the above-described effect, it is not possible to reduce the shock caused by the torsional stress on the front drive shaft in the parking state.
Publication 2 teaches a technique of producing a vibration controlling torque by detecting the degree of torsional vibration produced when the operation of the parking lock unit is complete, and producing a torque corresponding to the amplitude of the detected vibration. With the technique of Publication 2, directed to the above-described effect, it is not possible to inhibit the initial shock since a vibration controlling torque is not produced until the torsional vibration actually occurs.